error : PLEASE HELP !!!

windows cannot access this file you may not have the appropriate permission ….. this is the error message which i get after i had updated my avg anti-virus software when i try using any of my desktop icons and almost whole of my control panel is also not working and also the msconfig command is giving me the same error, on safe mode things are fine and i don’t have any i.e enhanced security , windows xp sp 2 , many files blocked, what should i do ???? please help